Various clutching devices are used to selectively connect mechanical components together so that they can rotate at the same angular speed about a common axis, allowing torque and power to be transmitted from one component to the other. A friction clutch contains two sets of friction plates mounted respectively to driving and driven parts. It relies on friction force to transmit torque and power. Positive engagement clutches, such as dog clutches typically include a pair of jaws directed towards each other for engaging or disengaging the driving and driven parts.
U.S. Pat. No. 6,745,882, for example, describes a locking clutch in which a toothed member and a slide assembly which are connectable to drive and driven parts. The two members are movable between an engaged position in which the clutch transfers power and/or torque to the driven part and a disengaged position in which power and/or torque is not transferred. The toothed member comprises a cylindrical surface and a plurality of teeth spaced about and extending from the cylindrical surface. The slide assembly comprises a body having a circumferential surface with a plurality of channels formed in said surface. Slide members are received in the channels to be movable between an extended position in which they can engage the teeth of the toothed member and a retracted position in which they do not engage the teeth of the toothed member. A resilient member biases the slide members to their extended positions. The slide assembly can be formed so that the slide members move either axially or radically relative to the slide assembly body.
GB Patent No. 753,520 describes a clutch wherein a shaft is moved axially to engage a first set of splines with a second set of splines. The arrangement is such that if, when engagement is attempted, the first set of splines abut against the second set of splines a ring is rotated so that the first set of splines can be guided between the second set of splines
Similar devices are discloses in U.S. Pat. Nos. 3,289,486 and 3,481,437.